Electrical discharge lamp



.3u-dy 3,1934, L. K. MARSHALL ELECTRICAL DISCHARGE LAMP Original FiledApril 22. 1951 2 Sheets-Sheet l N @ZM/gm ATTRZY Juy 3, E934 n.. K.MARSHALL ELECTRICAL DISCHARGE LAMP Original Filed April 22, 1931 2Sheets-Sheet 2 fa j] l ff VENR ATTMY Patented July 3, 1934 l UNITEDSTATES PATENT OFFICE ELECTRICAL DISCHARGE LAMP Laurence K. Marshall,

Cambridge, Mass., as-

Application April 22, 1931, Serial No. 531,895 Renewed November l, 193317 Claims.

'Ihis invention relates to electrical discharge lamps, and it hasespecial relation to lamps which are adapted to be energized by highfrequency currents. I

Among the objects of my invention is the provision of such a lamp inwhich both the source of light and the source of electrical oscillationsare combined in a single tube.

The foregoing and other objects of my invention will be best understoodfrom the following description of exemplications thereof, referencebeing had to the accompanying drawings, wherein:

Fig. 1 is a view partly in section of a device incorporating myinvention;

Fig. 2 is a cross-section taken along line 2 2 of Fig. l;

Fig. 3 is an enlarged cross-section taken along line 3-3 of Fig. `1;

Fig. 4 is a diagrammatic showing of the circuits involved in Fig. 1;

Fig. 5 is a view similar to Fig. 1 showing a slightly dierent form oflamp embodying my invention;

Fig. 6 is a diagrammatic showing of the circuits involved in Fig. 5; and

Fig. 7 is a view similar to Fig. 1 of another embodiment of myinvention.

In lamps which are energized by high-frequency, electrical currents, itis necessary to pro- Vide an oscillator to serve as the source of these,

high-frequency currents. The use of a separate tube and associatedcircuit as the oscillator renders the utilization of the lampcumbersome, due

to the considerable amount of auxiliary apparatus. In accordance with myinvention I avoid the disadvantages of a large amount of auxiliaryapparatus and secure various other benefits by combining in a singletube or unit both the oscillator and the light-generating elementitself.

' In the exempliication shown in Fig. 1, the light-generating element isindicated as l. This light-generating element preferablyv comprises athin-walled, quartz globe or container which A contains a lling of a gasor vapor which possesses the desired spectral properties when excited byan electrical discharge. As such gaseous filling I prefer to use amixture of a vapor, such as that of zinc, mercury, or the like, and arare gas, such as argon, at a pressure of about several millimeters. Ofcourse it is clear that various other gases, vapors, or mixtures thereofmay be used.

An electrical discharge is produced within the container 1 by means of acoil 2 surrounding said container. This coil is fed with high-frequencycurrents from an oscillator.

With various vapors, the desired vapor pressure for operation of thelamp occurs at a temperature considerably higher than room tem- 00perature. The temperature of the container 1 which encloses the vapor israised by the heat liberated by the discharge in the vapor. 'Ihus it isoften desirable to prevent excessive loss of heat by conduction from thewalls of the container l 55 in order that the proper temperatureand-vapor pressure may be maintained in said container. By enclosing thecontainer in an evacuated space, said container is thereby effectivelyinsulated against excessive loss of heat by conduction from its walls. Iaccomplish this result in the exemplication shown in Fig. 1 by enclosingthe container 1 in the evacuated envelope 3. This envelope also containsthe plate 6, the grid 7 and the lament 8, which are arranged as in theordinary three-elements vacuum tube. These electrodes form part of theoscillator which feeds the coil 2.

In addition to securing compactness and heat insulation, it is alsodesirable to prevent radia- 30 tion of the oscillation energy used forinducing high radiation in lamps of the type involved. The more confinedthe space in which the oscillator is built and the shorter the leadsconnecting the various parts of that oscillator, the less will be thetendency for radiation of the oscillations to occur. I secure bothprotection against such radiation and additional compactness by mountingpractically all of the elements of the oscillating circuit within theenvelope 3.

The various elements within the envelope 3 are supported as follows:

The envelope is provided with a reentrant stem 4 carrying a press 5 atits upper end. The plate 6 is supported by two plate standards 9 and l095 sealed in the press 5. The grid 7 is carried by two grid standards 11and 12 supported by wires 13 and 14 also sealed in the press 5. Thelament 8 is connected to and supported by the two lament leads 15 and16. The press 5 is formed 100 with a plurality o f wings extending inmore than one plane, the standards 9, 10, 11 and 12, and the wires 13,14, 15 and 16 being sealed in the wings in one plane. A plurality ofstandards are sealed in the wings in another plane. 0f these addi- 10517'. This insulating plate maintains the upper n.

vis diagrammatically shown in Fig. 1.

end of these standards in fixed relation with one another.

The container 1 is supported within the envelope 3 by the two supportingarms 18 and 19. These two arms are rigidly connected to two plates 20and 21, respectively. These plates are clamped tightly onto the stem 4by means of a clamping ring 22. The plates 20 and 21 are maintained aslight distance apart at their ends (see Fig. 2), and are insulated fromthe clamping ring 22 by a layer of insulation 23. Thus the two arms 18and 19 are electrically insulated from one another. These two arms carrysupporting members 24 and 25 at their upper ends. These supportingmembers carry the container 1. The opposite ends of coil 2 are connectedto the two arms 18 and 19, respectively. Thus these two arms afford amechanical support for the container 1 and the coil 2, and also serve aselectrical connections to said coil. The two condensers 26 and 27 arefastened to and supported by the two arms 18 and 19, respectively. Thesecondenser-s are each formed by two curved conducting plates 60 and 61(see Fig. 3), separated from each other by a layer of insulation 62.These plates are held together by a plurality of rivets 28. Each rivetis insulated from the plate 60 by an insulating bushing 63, but is inelectrical contact with the plate 61. Each rivet is provided with atongue 64 by which it is welded to its respective arm 18 or 19. Thus thearms 18 and 19 are in electrical connection with the inner plate 61 andinsulated from the outer plate 60 of the condensers 26 and 27,respectively. A unit consisting of an inductively-wound coil 29 inseries with a resistance 30 is supported at the upper ends of thestandards 11 and 17. This unit is diagrammatically shown in Fig. 1. Oneend of said unit is electrically connected to the grid standard 11 andthe other end is electrically connected to the plate standard 17. Thestandard 11 is also electrically connected by means of a conductor 32 tothe outer plate 60 of the condenser 26, while the standard 17 isconnected by a conductor 33 to the filament lead 15. The plate standard10 is electrically connected to the outer plate 60 of the condenser 27by means of a conductor 34. The filament leads 15 and 16 are providedwith conductors 35 and 36 leading to the exterior of the envelope 3. Theplate standard 10 is likewise provided with a conductor 37 leading tothe exterior of said envelope. In series with the conductor 37 is aninductively-wound coil 38 which The conductors 35, 36 and the outer endof the coil 38 are connected to three points 39, 40 and 41,respectively, of an auto-transformer 42. This transformer may be in theform of a toroidal coil wound upon a closed iron ring.

In order to make the unit complete in itself,

the transformer is carried in the base,42 which is mounted on the lowerend of the envelope 3, while the coil 38 is supported within thereentrant stem 4 of said container. The base 42 carries a socket 44 atits outer end. This socket comprises a shell contact 45 and a centercontact 46 adapted to make electrical connections with the two terminalsof an ordinary electric lamp socket. 'I'hese contacts 45 and 46 areconnected respectively to two points 47 and 48 on the transformer 42.

The circuits involved in Fig. 1 can be more clearly understood byreference to Fig. 4. The transformer 42 is fed with alternating currentat the two points 47 and 48. The portion between the points 39 and 40are used to furnish heating current to the filament 8. The entiretransformer between the points 39 and 41 is used to impress acomparatively high voltage between the filament 8 and the plate 6. 'I'hegrid 7 is connected to the filament 8 through the leak resistance 22.This resistance is of a high value, of the order of about 100,000 ohms.The circuit comprising the grid 7, the plate 6, the condenser 27, thecoil 2, and the condenser 26 constitute an oscillatory circuit. Theinductance 32 is used to prevent the oscillatory currents from flowingthrough it into the filament circuit. The inductance 38 is likewise usedto prevent the passage of oscillatory currents.

When the filament 8 is energized and the source of potential isconnected in the circuit in such a direction as to make the plate 6positive with respect to the filament, oscillations will be set up inthe oscillatory circuit. Since I have shown the circuit in Fig. 4 asbeing fed from an alternating current source, the above condition willnot be true during one-half of each alternating voltage cycle. However,conditions under which the tube will oscillate will exist during theother half of each alternating voltage cycle, and oscillatory currentswill be set up in the oscillatory circuit during each of said halfcycles. Thus when a source of alternating potential is connected betweenthe points 45 and 46, oscillatory currents will flow in the coil 2.These currents will induce an electrical discharge in the gas within thecontainer 1. Upon such a discharge taking place, a light having thecharacteristic spectral properties of the gas will be emitted.

The light shown in Fig. 1 is entirely complete in itself. It can beoperated merely by inserting it directly in an ordinary light socket fedwith alternating current.

Instead of using an alternating potential to energize the tube, a directpotential could be used. In that case the oscillations produced by thetube would be continuous rather than intermittent as in the case of analternating potential. Furthermore, the use of direct current wouldeliminate the necessity of such a transformer as is disclosed in Fig. 1.

Although I have described the interior of the envelope 3 as beingevacuated, it may be desirable in certain instances to provide a gaseousfilling within said envelope. For example, in some cases it is desirableto operate the lamp at extremely high intensities for purposes ofincreasing the efliciency thereof. In such cases the amount of heatliberated within the discharge becomes excessive and the temperature ofthe container 1 would tend to rise to an excessively high value. Underthese conditions it is no longer desirable to insulate the container 1against the loss of heat, but some means for conducting the heat awayfrom the walls thereof is advisable. By surrounding the container 1 withgases of high heat conductivity, the heat liberated by the discharge israpidly conducted to the walls of the envelope 3. Since these walls havea considerably greater area than the walls of the container 1, the totalamount of heat conducted to them is rapidly dissipated into thesurrounding atmosphere.

The oscillator can be designed to operate very efficiently in such agaseous atmosphere. This can be accomplished, for example, by decreasingthe spacing between the electrodes to a point at which discharge pathsbetween them are of the order of the mean free path of the molecules inthe gas. The power output of an oscillator in a gaseous atmosphere isordinarilyl considerably greater than a similar oscillator-operated in avacuum.

In the case of a gaseous filling within an en-v velope 3, it isdesirable to prevent a discharge being induced therein by the coil 2.This may be accomplished, for example, by maintaining the pressure ofthat gas sufficiently high so that a discharge is not initiated withinthat gas by the coil 2. It is further possible to prevent such adischarge from occurring by making the distance between the walls of thecontainer 1 and the envelope 3 of small dimensions and the coil 2 beingplaced in this space. In such a case there is very little tendency for adischarge, due to the currents in coil 2, to occur outside of thecontainer 1.

In order to cut down on the loss of light caused by radiations fallingupon the coil 2, this coil is provided with a highly polished surface.lSince the coil is either in a vacuum or else in an atmosphere which isinert with respect to the surface of said coil, this polished surfacewill keep indefinitely without tarnishing.

Instead of mounting all of the elements of the oscillatory circuitWithin the envelope 3, the structure of the tube can be considerablysimplied byv merely mounting the electrodes of the oscillating tube, thelight-generating element and the inducing coil within the envelope. Thisis the structure which is shown in Fig. 5. Also instead of using theparticular circuit, as shown in Fig. 1, any other suitable oscillatorycircuit may be used. Such an` alternative circuit is used in Fig. 5,which circuit is shown diagrammatically in Fig.

In Fig. 5 is shown a light-generating element 101 which contains agaseous filling similar to that in the container 1. This container isvenergized from a coil 102 fed from an oscillator. The oscillatorincludes the plate 106, grid 107, and the lament 108 arranged as in theordinary three-element vacuum tube. The coil 102 and the threeelectrodes 106, 107 and 108 are mounted in the press 105 on thereentrant stem 104 of the envelope 103. The envelope 103 is evacuatedand also encloses the container 101. This container is supported by thetwo arms 118 and 119 projecting from the clamping ring 122, which ringis clamped onto the stem 104. The coil 102 is supported by two standards123 and 124 also sealed into the press 105. The electrodes 106, 107 and108 are provided with standards in the same manner as shown for theelectrodes in Fig. 1. The upper ends of the electrode standards projectthrough an insulating plate 117 which retains these standards in xedrelation with one another. In addition, the arms 118 and 119, and thestandards 123 and 124 also project through this plate which serves as anadditional support for these members. The standard 124 is electricallyconnected With one of the plate standards by means of the wire 125. Thestandard 123 is provided with a conductor 126 extending to the outsideof the envelope 103. The grid 107 and the plate 106 are provided withsimilar conductors 127 and 128, respectively. Two filament lead-inconductors 129 and 130 also leading outside of the envelope 103 areprovided. The conductors 126 to 130, inclusive, are connectedrespectively to the five contact prongs 131 to 135,`

pleted by connections external to the tube. A condenser 137 is connectedbetween the contact prongs 131 and 133. The filament is energized by aheating transformer 138, the secondary 139 of which is connected to thetwo contact prongs 134 and 135. From a point intermediate the ends ofthe secondary 139, a conductor 140 leads to the negative end of a sourceof potential, such as a battery 141. The positive end of this battery isconnected to the contact prong 131. The grid 107 is connected to thecathode by means of a connection extending from the contact prong 132 tothe conductor 140. In this connection is placed a high-resistance leak142 shunted by a condenser 143. The grid and plate circuits are coupledby means of two coils 145 and 146 which are placed in inductive relationwith one another. The coil 145 is placed in the external grid circuit,as shown, while the coil 146 is placed in the external series circuit,including the condenser 137. The oscillatory circuit, as is most clearlyseen from Fig. 6, comprises the coil 102 and the condenser 137.

When the filament 108 isl energized and the battery 141 connected,oscillations will be produced in the oscillatory circuit, and theoscillatory currents flowing in the coil 102 will induce a luminousdischarge within the light-generating element 101.

Since the amount of apparatus outside of the tube, as shown in Fig. 5,is very small, the entire ,device can be made quite compact. The outsidesame member which is adapted to receive the base 136.

When the electrodes of the oscillator are operated in a gaseousatmosphere, instead of using a separate container surrounding a separategas in which the light-generating discharge is maintained, the sameatmosphere which surrounds the oscillator electrodes may be used as thesource of light. Also various arrangements of these electrodes may beused in order to more eficiently take advantage of the greater outputavailable from a gaseous oscillator. In the exemplifcation shown in Fig.7, I have illustrated a lamp of this kind.

A transparent envelope 200 is formed with a reentrant stem 201 carryinga press 202 at its upper end. This press supports a number of electrodescomprising an indirectly heated cathode 203, a screen electrode 204, agrid 205, and an anode 206, all concentrically arranged. The cathode 203is provided with an internal heating filament, not shown, one end ofwhich is connected to a supporting standard 207 sealed in the press 202.'Ihe electron-emitting element of the cathode comprises the usual coatedmetallic sleeve. The other end of the heating filament is connected tothis sleeve, and said sleeve is provided with a conductor which isconnected to a supporting standard 208 also sealed in the press 202. Thescreen electrode 204, the grid 205, and the anode 206 are electricallyconnected respectively to the three standards 209, 210 and 211, all ofwhich are sealed in the press 202. The envelope 200 is filled with asuitable gas or vapor which may be, for example,` mercury. At 212 I haveindicated a drop of mercury which furnishes the requisite vapor. Theelectrodes 204, 205 and 206 are closely spaced from each other at adistance of the order of the mean free path of the molecules in thevapor surrounding them. Such an arrangement of the electrodes is basedon and operates in accordance with the description of the gaseousdischarge tube contained in the application of James D. Le Van, SerialNo. 447,495, filed August 25, 1930. Insulating plates 213 and 214 areused to support and maintain the relative position oi.' the variouselectrodes. The plate 213 extends substantially entirely across theenvelope 200, thereby separating the upper portion of said envelope fromthe lower portion thereof. This prevents the ionized discharge occurringin the light-generating portion 220 from passing into the portioncontaining the electrodes. The standards 207 and 208 are provided withconductors 215 and 216 leading to the exterior of the tube. Thestandards 209, 210 and 211 are likewise provided with external lead-inwires 217, 218 and 219. The envelope 200 is provided with alight-generating portion 220 and an electrode-containing portion 221 atone side thereof. A coil 222 surrounds the light-generating portion 220,and is adapted to produce a luminous discharge therein when fed byoscillator currents.

One of the circuits with which the tube, as shown in Fig. 7, can be usedis illustrated in that figure. A source of heating current, such as atransformer 223, is connected between the two cathode leads 215 and 216.A regulating resistance 224 is provided in series with one of said leads216. A source of potential, such as a battery 225, is connected inseries with a regulating resistance 227 between the lead-in wires 217and the conductor 215. The grid 205 is connected through its lead-inwire 218 to a radio-frequency choke 228 and a high-leak resistance 229to the lead-in wire 217 of the screen electrode 204. The anode 206 islikewise connected through its leadin wire 219, radio-frequency choke230, and a source of potential, such as a battery 231, to the lead-inwire 217 of the screen electrode 204. The opposite ends of the coil 222are connected through the two condensers 232 and 233 to the lead-inwires 219 and 218 respectively of the anode 206 and the grid 205.

The operation of the circuit and tube, as shown in Fig. 7, is briefly asfollows:

The current from the heating transformer 223 raises the temperature ofthe cathode 203 to a point at which it emits electrons. The battery 226establishes a potential between the cathode 203 and the screen electrode204 which is sufficient to produce an ionizing discharge in the gasbetween said electrodes. This discharge produces large numbers ofelectrons and positive ions in said discharge space. The electrons passrapidly through the meshes of the screen electrode 204, and enter thespace between the electrode 204 and the anode 206. Since the anode 206is at a positive potential with respect to the screen electrode 204, dueto the battery 231, the electrons which pass through said screenelectrode are attracted toward said anode. Some of the electrons passthrough the meshes of the screen 204 with sufficient initial velocity sothat the additional velocity gained by falling through the potentialestablished by the battery 231 is sufficient to ionize some of the gasin the space between the electrodes 204 and 206. Thus the few positiveions are created in that space which tend to diminish the space chargebetween said electrodes. Since, however, the space between saidelectrodes is of the order of the mean free path of the vapor,substantial ionization will not occur in said space and the conductionbetween said electrodes will be maintained primarily by the stream ofelectrons coming through the meshes of the screen 204. 'I'he grid 205placed between the screen electrodes 204 and 208 controls the dischargebetween these electrodes exactly in the same manner as in the ordinarythree-element vacuum tube. It will be noted that the oscillatingcircuit, of which the coil 222 forms a part, is exactly the same as thatshown for the device as illustrated in Fig. 1. Thus when the tube inFig. 7 is energized in the manner described, oscillations will beproduced in the oscillatory circuit. which oscillations appearing in thecoil 222 will induce a discharge in the atmosphere within thelight-generating region 220.

It is of course possible in the device as shown in Fig. 7 in a mannersimilar to that described ln Fig. 1, to mount the various elements ofthe oscillating circuit within the envelope 200 in order to produce amore compact device. However, since the amount of apparatus outside theenvelope 200 is not very extensive even in the arrangement as shown inFig. 7, it can be mounted as a compact unit associated with the envelope200 itself. Although I have shown the envelope 22 as being exposed tothe outer atmosphere, it may sometimes be desirable to mount thisenvelope together with 100 the coil 222 in an outer evacuated orgas-filled envelope in a manner similar to that described for Figs. 1and 5. The advantages of so enclosing the envelope has been set forth inthe explanation of these two figures.

The invention is not limited to the particular details of construction,materials or processes described above, as many equivalents will suggestthemselves to those skilled in the art. It is accordingly desired thatthe appended claims be 110 given a broad interpretation commensuratewith the scope of the invention within the art.

What is claimed is:

1. A lamp comprising a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, an oscillator,including a cathode, an anode and a control electrode for generatingsaid oscillatory currents, a sealed envelope enclosing said gaseousatmosphere and said electrodes, said envelope being provided with aspace adjacent to and clear of said electrodes in which said luminousdischarge is adapted to take place, and means for separating said spacein which said luminous discharge is adapted to take place from the spacecontaining said electrodes.

2. A lamp comprising a sealed container filled with a gaseous atmospherein which a luminous discharge is adapted to be maintained by oscillatorycurrents, an oscillator for generating said 130 oscillatory currents,said oscillator including a cathode, an anode, and a control electrode,and a sealed envelope enclosing said container and said electrodes.

3. A lamp comprising a sealed container filled 135 with a gaseousatmosphere. a coil adapted to be fed with oscillatory currentsassociated with said container, an oscillator for generating saidoscillatory currents, said oscillator including a cathode, an anode, anda control electrode, and a sealed envelope enclosing said container,said coil, and said electrodes.

4. A lamp comprising a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by high frequency currents, an oscillatorfor generating said oscillatory currents, said oscillator including-acathode, an anode, and a control electrode, and an oscillatory circuitassociated therewith, said oscillatory circuit including capacity andinductance elements, and a 150 sealed envelope enclosing saidatmosphere, said electrodes, and all of the capacity, and inductanceelements of said oscillatory circuit.

5. A lamp comprising a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents. an oscillator forgenerating said oscillatory currents, said oscillator including acathode an anode, and control electrode, and an oscillatory circuitassociated therewith, a voltage-dividing means for supplying voltages ofthe proper potential to said oscillator, a single unitary tubeincorporating all of the foregoing elements, a base on said tube, acouple of contacts on said base connected to said voltage divider, saidcontacts being adapted to be connected to the terminals of a source ofpotential.

6. A lamp comprising a sealed envelope containing a gaseous atmosphere,an oscillator including a cathode, an anode and a control electrodebetween them; said electrodes being mounted within said container insaid gaseous atmosphere, said cathode and anode being spaced apart adistance of the order of the mean free path of the molecules in the gas,high frequency means for maintaining a luminous discharge in saidatmosphere, and means for supplying oscillatory currents from saidoscillator to said high frequency means.

7. A lamp including a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, an envelopeenclosing said atmosphere, a cathode and an anode within said envelope,a control electrode for controlling a discharge between said cathode andanode, said cathode, anode and control electrode being part of anoscillator for generating said oscillatory currents, and means forhermetically separating the space containing said atmosphere from thespace containing said cathode and anode.

8. A lamp including a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, an envelopeenclosing said atmosphere, a cathode and an anode within said envelope,a control electrode for controlling a discharge between said cathode andanode, said cathode, anode and control electrode being part of anoscillator for generating said oscillatory currents, and means forhermetically separating the space containing said atmosphere from thespace containing said cathode and anode, the space containing saidcathode and anode being highly evacuated.

9. A lamp including a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, an envelopeenclosing said atmosphere, a cathode and an anode within said envelope,a control electrode for controlling a discharge between said cathode andanode, said cathode, anode and control electrode being part of anoscillator for generating said oscillatory currents, means forhermetically separating the space containing said atmosphere from thespace containing said cathode and anode, and a gas in the spacecontaining said cathode and anode, said cathode and anode being spacedapart a distance of the order of the mean free path of the molecules insaid gas.

10. A lamp including a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, a sealed envelopeenclosing said atmosphere, an oscillator for generating said oscillatorycurrents, said oscillator including an electrode, a cooperating anode,and a control grid between said electrode and anode, said electrodebeing such that electrons pass from it into the space between saidelectrode and said anode, said electrode and anode being within saidgaseous atmosphere at a distance of the order of the mean free path ofthe molecules in said atmosphere from each other.

11. A lamp including a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, a sealed envelopeenclosing said atmosphere, an oscillator for generating said oscillatorycurrents, said oscillator including an electrode, a cooperating anode,and a control grid between said electrode and anode, said electrodebeing such that electrons pass from it into the space between saidelectrode and said anode, said electrode and anode being within saidgaseous atmosphere at a distance of the order of the mean free path ofthe molecules in said atmosphere from each other, said envelope beingprovided with a space adjacent to and clear of said electrodes in whichsaid luminous discharge is adapted to take place.

12. A lamp including a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, a sealed envelopeenclosing said atmosphere, and an oscillator for generating saidoscillatory currents, said oscillator including a cathode, a screenelectrode, a cooperating anode, and a control grid between saidelectrode and anode, said screen electrode and anode being Within saidgaseous atmosphere at a distance of the order of the mean free path ofthe molecules in said atmosphere from each other, said cathode beingspaced from said screen electrode so as to support an ionizing dischargebetween said cathode and said screen electrode, said screen electrodebeing provided With openings, whereby electrons pass from the dischargespace between said cathode and screen electrode to the space betweensaid screen electrode and said anode.

13. A lamp comprising a gaseous atmosphere in which a. luminousdischarge is adapted to be maintained by oscillatory currents, anoscillator including a set of electrodes for generating said oscillatorycurrents, and a sealed envelope enclosing said gaseous atmosphere andsaid set of electrodes, said envelope being provided with a limitedportion in which said luminous discharge is adapted to take place andsaid set of electrodes in said envelope lying entirely outside of saidlimited portion of said envelope, the space of said luminous gasdischarge being hermetically segregated from the space enclosing saidset of electrodes.

14. A lamp comprising a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, an oscillatorincluding a set of electrodes for generating said oscillatory currents,and a sealed envelope enclosing said gaseous atmosphere and said set ofelectrodes, said envelope being provided with a limited portion in whichsaid luminous discharge is adapted to take place and said set ofelectrodes in said envelope lying entirely outside of said limitedportion of said envelope, the space of said luminous gas discharge beinghermetically segregated from the space enclosing said set of electrodes,and the pressure in the space of said set of electrodes beingsubstantially lower than in the space of said gas discharge.

15. A lamp, including a gaseous atmosphere, in which a luminousdischarge is adapted to be maintained by oscillatory currents, a sealedentrode between said anode and said cathode surface. the distancebetween said cathode and anode surface being of the order of the lmeanfree path of a. molecule in said gas. means for supplying electronsthrough said cathode to the space lying opposite the anode, and barriermeans for preventing entrance of said electrons into spaces between saidset of electrodes through which extend electrostatic ileld pathssumciently long to produce an independent discharge in said space.

16. A lamp comprising a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory currents, an oscillatorincluding a set of electrodes for generating said oscillatory currents,and a sealed envelope enclosing said gaseous atmosphere and said set ofelectrodes, said envelope being provided with a limited portion in whichsaid luminous discharge is adapted to take place and said set ofelectrodes in said envelope lying entirely outside of said limitedportion of said envelope.

17. A lamp comprising a gaseous atmosphere in which a luminous dischargeis adapted to be maintained by oscillatory frequency, an oscillatorincluding a set of electrodes for generating said oscillatory currents,and a sealed envelope enclosing said gaseous atmosphere and said set ofelectrodes, the device having the said set of electrodes ,lying withinone portion of the envelope and being adapted to have the luminousdischarge take place within another portion of the envelope.

LAURENCE K. MARSHALL.

